Seagate Technology Incorporated

Matthew Chad Burton

Jason Dale Gregg

Timothy Ted Walker

Robert Matousek

David Charles Waugh

Ke Du

William C Little

A programmable controller and method for correcting operation of a read/write head in a disc drive having an embedded servo system in which the head is not reading correctly operates by applying a write current to the failed head only after the head is positioned over an area of a disc that does not have useful data thereon. Movement and position of the head that is not reading correctly is determined from a signal from an adjacent head. The adjacent head is used to read servo information. After the adjacent head has provided servo information and the controller repositions the adjacent head in a safe area, a write current is applied to the failed head to realign the head without the potential of adversely impacting data stored in adjacent tracks.

Apparatus and method for wiggle recovery in a disc drive having an embedded servo

Method and apparatus for moving a head of a disc drive from an initial position to a destination position on a recording surface of a rotatable disc by generating and applying a model reference current to an actuator motor. A servo circuit includes a current profile generator which generates a baseline reference current profile. A gain calculator calculates first and second gain factors in relation to an initial velocity of the head. A gain block generates the model reference current by applying the first gain factor to a first portion of the baseline reference current profile used to accelerate the head and subsequently applying the second gain factor to a second portion of the baseline reference current profile used to decelerate the head, wherein the first and second gain factors have different respective magnitudes to compensate for a nonzero initial velocity of the head.

Self tuning model reference controller in a disc drive

Apparatus and method for compensating for position signal distortion during a disc drive seek. A disc drive has first and second data recording surfaces on which tracks are defined, a moveable actuator which supports first and second magneto-resistive heads, and a servo circuit which applies current to an actuator motor to position the heads. During a seek in which the first head is moved from an initial track to a first destination track, upon loss of transduced servo data from the first data recording surface indicative of radial position of the head, the servo circuit switches from the first head to the second head and applies current to the actuator motor to move the second head to a known radial position with respect to the first destination track while transducing servo data from the second data recording surface. The servo circuit subsequently switches back to the first head to position the first head over the first destination track.

Position signal distortion compensation during a disc drive seek

Disclosed is a method of compensating for non-optimal operating conditions during a sine seek operation. A disc drive with a seek controller provides a feedforward signal to an actuator during a portion of the operation of an actuator and provides a velocity signal during another portion of operation of the actuator. The controller also stores a velocity error switch point. If it is determined that the feed forward signal is lower or higher than a first nominal value, then the feed forward signal provided by the controller is adjusted. Furthermore, if it was determined that the feed forward signal is lower than the first nominal value, the velocity error switch point is decreased.

Sine seek adaptation at voltage and temperature margins

Apparatus and method for optimizing a gain of a disc drive servo circuit, the gain used to control the magnitude of current applied by the servo circuit to a voice coil motor to position a head adjacent tracks of a disc. The servo circuit includes a servo processor which selects an initial value of the gain, and then proceeds to perform a gain convergence operation wherein the head is repeatedly moved across the disc over a number of passes and position error is accumulated during each pass. The accumulated position error is used along with a scale factor to converge the gain from an initial gain value to a final, optimal gain value. The scale factor is variable and is also converged over the successive number of passes from an initial value to a final, nominal value, in order to decrease the time required to obtain the final, optimal gain value.

Servo gain optimization using a variable convergence factor

A method and system of filtering an unfiltered servo torque table of a disc drive where a plurality of data points are added to the beginning and end of the unfiltered servo table and the table is then shifted by a valve and then filtered.

Method and system for filtering force constant table for accurate torque modeling

An apparatus and method for determining the configuration of a disc drive head-disc assembly (HDA). The HDA includes an array of rotatable discs and an actuator adjacent the discs, with the actuator supporting a maximum number of heads in a fully populated configuration and a reduced number of heads in a depopulated configuration. Each head is disposed at a unique head position. During each spin-up of the disc drive, a servo circuit determines an impedance of a selected head position having a head when the disc drive is fully populated, but not when the disc drive is depopulated. The servo circuit identifies this configuration of the HDA in relation to the determined impedance, and initializes the drive accordingly. The drive then identifies the configuration of the HDA based on the value of the impedance, initializing the drive accordingly.

Reduced head population detection in a disc drive

An apparatus and method for optimizing detection thresholds used to identify addresses of tracks in a disc drive having a head and a disc upon which a plurality of tracks are defined, the tracks including track address fields in which track address information is stored. A comparator is provided which generates track address sequence signals in response to a corresponding plurality of readback signals obtained as the head is maintained in a fixed relationship to a selected track. A demodulator identifies erroneous track address sequence signals therefrom and increments a count in an accumulator for each detected, erroneous signal. A detection threshold circuit sequentially provides the comparator with a set of detection thresholds from a population of detection thresholds, each of which are used in turn by the comparator. An optimal set of thresholds is thereby selected for use by the disc drive in accordance with the relative number of erroneous track address sequence signals accumulated for each of the detection thresholds from the population.

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Edmond, OK, United States of America

Matthew Chad Burton